QTL Analysis of Morpho-Agronomic Traits in Garden Asparagus (<i>Asparagus officinalis</i> L.)

In order to understand the genetic control of quantitative agronomic traits in garden asparagus, we performed a quantitative trait loci (QTL) analysis. A population (n = 167) derived from a cross between a female and male plants was evaluated for morpho-agronomic traits over three years. Interval mapping (IM) and restricted multiple QTL mapping (rMQM) analysis was applied, and 18 QTLs were detected. QTLs were located in two linkage groups (LG): 5 in LG5 and 13 in LG6. The physical position of markers of both groups was mapped onto the reference genome through BLAST analysis. LG5 and LG6 match with chromosome 1 (sex-determining chromosome) and chromosome 5, respectively. Haplotypes of both chromosomes of the heterozygous parent and their progeny were obtained, and a bin map was developed. Bins were used to map the QTLs on the reference genome and to perform the association analysis with the morpho-agronomic traits. Two major and stable QTLs over the years (R2 > 10%) for number of stalk and earliness were mapped in the end of chromosome 1 into a bin that spans 3.25 Mb and includes the sex-determination locus. In chromosome 5, some QTLs were located in the center of chromosome for the year 2016. Branching is tightly regulated by both internal factors (such as plant hormones) and external factors (such as light conditions). QTLs for branching height and earliness were detected in a bin that spans 4.96 Mb. Functional annotation of genes within the two bins revealed candidate genes with potential roles in SA and light signaling and photomorphogenesis pathways that may be involved in branching and/or tillering. This is the first study providing the identification of genomic regions associated with yield-related morpho-agronomic traits in asparagus